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Biological Control


It is the position of the Weed Science Society of America (WSSA) to promote the development and implementation of biological control methods as a component of weed management strategies.

Weeds are estimated to cause more than $40 billion in annual global losses through degraded agricultural and silvicultural productivity, reduced access to land and water, impaired esthetics, and disruption of human activities and well-being.  Manual removal, mechanical cultivation, cultural practices, or chemical herbicides can control weeds.  However, use of physical and/or chemical methods of weed control alone is not feasible, desirable, or sufficient in every situation.

Biological control of weeds is broadly defined as the use of an agent, a complex of agents, or biological processes to bring about weed suppression.  All forms of macrobial and microbial organisms are considered as biological control agents.  Examples of biological control agents include, but are not limited to:  arthropods (insects and mites), plant pathogens (fungi, bacteria, viruses, and nematodes), fish, birds, and other animals.  Biologically based weed management is a much broader category of approaches that may include gene modification, genetic processes, and gene products.  Human activities intended to remove weeds directly or indirectly, such as hand-weeding and burning, deliberate uses of plant competition, allelopathy, and cultural and soil management practices that alter the biotic balance of soil are considered important adjuncts to biological control in integrated weed management systems.

Biological control has been used successfully as a practical and economically affordable weed control method in many situations.  While there has been an increase in interest in biological control over the past 20 years, earlier instances of its use date back to 200 years.  Classical biological control, which is biological control of non-native invasive weeds with natural enemies originating from the native range of the weed, has proven a viable strategy for managing weeds in areas subjected to low-intensity management, such as rangelands, forests, preserved natural areas, and some waterways.  The use of an inundative method, also called the bioherbicide strategy, where an organism is applied to achieve rapid reduction in weed populations, has also proven successful in some instances.  In the future, pathogens may also be used to introduce or alter specific genes to control growth, flowering, seed set, and/or competitiveness of weeds.

It is imperative the next generations of weed scientists are trained in the principles and practices of biological weed control.  Weed science curricula must introduce students to the major groups of biological control agents and research methods.  Conservation and integration of biological control agents must be taught as one of the foundations of sustainable weed management.

It is the position of WSSA that biological control agents and methods are developed as weed control options to maintain sustainability in agriculture and for the protection of natural resources.  Biological weed control should be a component of integrated weed management systems consisting of multiple biological control organisms and judicious use of chemical, cultural, and physical methods.  It is essential to continue funding of research and development of biological weed control as a management option, to foster a commitment from federal, state, private, and public institutions to this option, and to increase emphasis on biological weed management in weed science curricula.  WSSA supports biological control of weeds with research presentations on this method of weed control at its annual meetings, a Biological Control of Weeds Committee to inform and enable its membership to focus on issues related to the biological control of weeds, and symposia and production of literature on the topic.

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